Caption: Animation of a skydiver showing the effects of gravity and drag on terminal velocity. After jumping, the skydiver accelerates due to gravity, at nearly 10 metres per second per second. However, the opposing force of drag due to air resistance also increases with speed, and when it balances gravity the acceleration stops and the velocity is steady. This is known as terminal velocity. The drag force is relative to a falling body's area perpendicular to the fall. When the parachute opens, the surface area greatly increases, reducing the terminal velocity to a level at which it is safe to land.